tools/url_check: Remove leading slash from openvpn (#536)

.hecat/url-check.yml

@@ -9,4 +9,4 @@ steps:
         - licenses.yml
       errors_are_fatal: True
       exclude_regex:
-        - '^https://community.openvpn.net/$' # DDoS protection page, always returns 403
+        - '^https://community.openvpn.net$' # DDoS protection page, always returns 403